help with hard drive

hi, please help, i have an external hd with its own power source, i think up to now i have done every thing right??? fromated hd installed games and installed usb loader on wii, it comes on, all games load up but with 20 mins or so it trips my wii out and blows the fuse in the plug, tryed it with another hd and done the same? so i tryed it on a friends wii and it worked fine? so i sold it to some one else and it done the same, blow the fuse, my wii is a 3.4 could it be bad ios??? hope some one can help thanx.